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Biomedical subjects

S Kito

Publications and source records attributed to S Kito.

At least 109 records · Page 6Linked to original sources
PubMed1986

Atrial natriuretic polypeptide-like immunoreactivity in the rat pituitary: light and electron microscopic studies.

Immunoreactive atrial natriuretic polypeptide (ANP) was investigated in the pituitary of rats by light and electron microscopy using the indirect immunofluorescence and peroxidase-antiperoxidase techniques. ANP-like immunoreactivity was present in 30-35% of anterior pituitary cells. These cells have two types of secretory granules being characteristic of rat gonadotrophin-storing granules, and were usually adjacent to the capillary endothelium. The results of this study suggest the co-occurrence of ANP and gonadotrophins in the anterior pituitary cells.

Animals↗
PubMed1986

A substance P-containing pathway from the hypothalamic ventromedial nucleus to the medial preoptic area of the rat: an immunohistochemical analysis.

The destruction of the hypothalamic ventromedial nucleus, which contains a group of substance P-like immunoreactive neurons, resulted in a marked ipsilateral reduction of these fibers in the medial preoptic area. To test if and to what extent the substance P-like immunoreactive neurons in the ventromedial nucleus project to the medial preoptic area, we applied a sensitive double-labeling method capable of detecting substance P-like immunoreactivity in neurons retrogradely labeled with biotin-wheat germ agglutinin following injection of the tracer in the medial preoptic area. The appearance of many double-labeled cells in the hypothalamic ventromedial nucleus provides strong evidence for the existence of a prominent substance P containing pathway from the ventromedial nucleus to the medial preoptic area. A few doubled-labeled cells were also seen in the lateral hypothalamus, which therefore seems to be an additional source of substance P-like immunoreactive fibers in the medial preoptic area.

Animals↗
PubMed1986

Enkephalin-like immunoreactive neurons and fibers in the ventromedial hypothalamic nucleus.

Enkephalin-like immunoreactive (ENK-IR) neurons and fibers in the rat ventromedial hypothalamic nucleus (VMH) were examined by light and electron microscopy using the peroxidase-antiperoxidase immunocytochemistry. There were groups of ENK-IR neurons present in the ventrolateral part of the VMH, and such neurons were scattered elsewhere. These neurons had perikarya 10-25 microns in diameter with moderately developed cell organelles and enfolded nuclei that were often distributed eccentrically placed in the cell. The perikarya and dendrites contained diffuse, large-cored vesicles (LCV) (60-230 nm with a predominance in the 60-80 nm). ENK-IR neurons received synaptic inputs on the soma and dendrites from unlabeled axonal boutons containing many small, clear vesicles and occasional LCV. The ultrastructural features of the ENK-IR cells in the VMH seemed to correspond to the "common cells" described by Millhouse. Dense ENK-IR fibers were distributed in this nucleus throughout the rostrocaudal and ventrodorsal areas. Axonal boutons containing numerous small, clear vesicles, and dispersed LCV generally made synaptic contacts with the cell bodies and dendrites of unlabeled neurons. The findings suggest that opioid peptides directly influence VMH neurons through synaptic contacts.

Animals↗
PubMed1986

Effects of somatostatin on muscarinic acetylcholine receptor binding in the rat hippocampus.

The authors noticed effects of somatostatin on muscarinic acetylcholine receptors (mAchR) in the rat hippocampus from binding experiments. Saturation experiments of 3H-oxotremorine-M-acetate (3H-oxo-M) buffered with Krebs-Henseleit solution revealed that there were two binding sites with very high and low affinities whose Kd values were 1.2 nM and 445.8 nM, respectively. Adding somatostatin in this incubation medium caused an increase in the Kd value of the high affinity binding site with no change in the Bmax value. As for the low affinity binding site, Kd and Bmax values were too large to determine the effect of somatostatin. The oxotremorine/3H-N-methyl-scopolamine competition experiments indicated the presence of two components of agonist binding sites. The inhibition curve after adding somatostatin fitted best to a single homogeneous binding site whose Ki value was consistent with the dissociation constant of the oxotremorine low affinity binding site. Therefore, it seems that somatostatin accelerates conformational changes of the oxotremorine high affinity binding site to the low affinity binding state. A single binding site with a Kd value of 30.9 nM was obtained by switching the buffer to Na-K phosphate solution. The affinity of this binding site was likewise inhibited by somatostatin. The inhibitory effect of somatostatin-28 was more marked than that of [D-trp8] somatostatin. The above-mentioned effects of somatostatin was limited to mAchR agonist binding.

Animals↗
PubMed1986

Effects of neurotransmitters or drugs on the in vivo release of dopamine and its metabolites.

The effects of neurotransmitters or drugs on the release of endogenous dopamine (DA) and extracellular levels of its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were examined in vivo by intracerebral dialysis. A dialysis tube was implanted stereotaxically through bilateral caudate nuclei of rats and perfused with the Ringer solution. Amounts of DA, DOPAC and HVA in the perfusates were measured by high performance liquid chromatography (HPLC) with electrochemical detection. The basal level of DA was 2.76 +/- 0.64 pg/min, whereas the levels of DOPAC and HVA were 218.7 +/- 20.7 and 142.4 +/- 10.6 pg/min, respectively. Apomorphine (4 mg/kg, i.v.) reduced the efflux of DA and its metabolites. Haloperidol (0.4 mg/kg, i.v.) did not change DA release and produced only a minor increase of its metabolites. This increase of metabolites was inhibited by pargyline. Met-enkephalin (10(-4) M), substance P (10(-4) M) and acetylcholine chloride (10(-4) M) added to the perfusing medium increased the release of DA. Met-enkephalin also increased the release of DOPAC. gamma-Amino-n-butyric acid (GABA, 10(-4) M) reduced the release of DOPAC and HVA when added to the perfusing medium. Thyrotropin releasing hormone (TRH, 5 mg/kg, i.v.) increased the release of HVA. These findings indicated that different mechanisms mediated effects of neurotransmitters or drugs on the release and metabolism of DA in the rat striatum.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Structure of the mutant prealbumin gene responsible for familial amyloidotic polyneuropathy.

Familial amyloidotic polyneuropathy (FAP) is a genetic disorder showing autosomal dominant inheritance. Amyloid fibrils of FAP patients from various origins have been shown to contain a prealbumin variant with Val30----Met30 substitution as a major component. However, the structure of the prealbumin gene responsible for the variation has not been characterized. We determined the complete nucleotide sequence of the prealbumin gene from a patient with the Japanese type of FAP. In comparison with a normal prealbumin gene sequence, the patient's gene was found to be carrying seven base substitutions. The substitution responsible for the Val----Met change was found in exon 2, as expected, and the others were in introns. Hybridization analyses of normal and FAP patient DNAs showed that the base substitution in exon 2 was specific for FAP but the others were polymorphic changes. It was concluded that the mutation responsible for the Val----Met change is the only base change specific for FAP in the prealbumin gene.

Amyloidosis↗
PubMed1985

Immunohistochemical localization of neurotensin and beta-endorphin in the rat anterior pituitary gland.

Nakane's enzyme-labeled antibody technique revealed that cells containing neurotensin-like immunoreactivity were widely distributed in the anterior lobe of the pituitary body. Immunohistochemical studies on serial sections showed that a part of neurotensin positive anterior lobe cells contained beta-endorphin-like peptide simultaneously. The results show that beta-endorphin and neurotensin occur together in certain pituitary cells and this is an evidence of coexistence of more than one peptide within one anterior pituitary cell.

Animals↗
PubMed1985

An enkephalinergic projection from the hypothalamic paraventricular nucleus to the hypothalamic ventromedial nucleus of the rat: an experimental immunohistochemical study.

The distribution and origins of enkephalin-like immunoreactive (ENK-IR) fibers in the nucleus ventromedialis hypothalami (vm) of the rat were examined using immunohistochemistry. A dense plexus was evenly distributed in the vm with no regional differences. A group of ENK-IR neurons was concentrated in the ventrolateral portion of the vm. The destruction of the hypothalamic paraventricular nucleus (pv) which contained numerous ENK-IR neurons, resulted in a marked decrease in ENK-IR fibers in the vm on the operated side. In addition, the destruction of the magnocellular portion of the pv, while leaving most of parvocellular portion intact, failed to substantially decrease the ENK-IR fibers in the vm, suggesting that these fibers originate from ENK-IR neurons located in the parvocellular portion of the pv. The present study further showed that the axons of these neurons first proceeded laterally to the perifornical area, next ran ventrolaterally to the ventrolateral portion of the anterior hypothalamic nucleus and finally turned medially to the vm.

Animals↗
PubMed1985

Leucine-enkephalin-like immunoreactive fibers in the medial preoptic area of the rat: their distribution and origin.

We studied the distribution of fibers with leucine-enkephalin-like immunoreactivity (L-ENKI) in the medial preoptic area (MPO) of the rat, and the origins of such fibers, using indirect immunofluorescence and a combination of a retrograde tracer with immunocytochemistry that we have developed. These fibers were very dense throughout the rostro-caudal part of the MPO. The distribution was uneven with the highest density in the lateral part. Destruction of the arcuate nucleus, which contains a group of L-ENKI neurons, resulted in the marked reduction of these fibers in the ipsilateral MPO, suggesting that most of these fibers originate in this nucleus. This was also suggested by the fact that injection of biotin-wheat germ agglutinin into the MPO labelled many neurons in the arcuate nucleus ipsilaterally. Simultaneous staining with antiserum showed that some of these neurons are L-ENKI.

Animals↗
PubMed1985

Autoradiographic studies on benzodiazepine receptor subtypes in the rat brain.

The technique of in vitro autoradiography which was developed by Kuhar and others was applied to the rat brain with use of 3H-flunitrazepam (flu) as a radioactive ligand. The cerebral cortex, hippocampus, substantia nigra and cerebellar cortex were rich in 3H-flu binding sites. To differentiate the benzodiazepine receptor (BZR) subtype, the authors used a type 1 specific ligand, either triazolopiridazine (CI 218872) or methyl-beta-carboline-carboxylate (beta-CCM), as an unlabeled displacer. The preparations were exposed on a 3H-sensitive film and then the film was developed. Computer-analysis of thus obtained autoradiographic pictures revealed that type 2 binding sites were distributed evenly within the rat brain, but with slight predominance in the hippocampus. After adding beta-CCM, no silver grains were noticed in the cerebellum and substantia nigra. These data meant that these two structures contained essentially type 1 BZR, while the hippocampus contained both type 1 and type 2 receptors. Autoradiographically, characteristic distribution of BZR represented by 3H-flu binding was considerably lost by adding a type 1 specific ligand, and this treatment caused the silver grains to be evenly distributed. These data suggest that the BZR which is directly associated with characteristic pharmacological actions such as anxiolytic and hypnotic effects is type 1, and type 2 binding sites have a less characteristic distribution pattern and might be pharmacologically less specific.

Animals↗
PubMed1984

A variant prealbumin-related low molecular weight amyloid fibril protein in familial amyloid polyneuropathy of Japanese origin.

Amyloid fibril protein with a molecular weight of 8K daltons, in addition to one of 16K daltons, has been isolated and characterized from an autopsy sample of a patient with familial amyloid polyneuropathy in a Japanese family from Ogawa Village, Nagano Prefecture. The component was shown to react with an antiserum to normal plasma prealbumin, as did the other. Following the purification by reverse phase liquid chromatography, it was digested with trypsin and the peptides, after the purification by HPLC were sequenced. The data showed that the component was a distinct fragment whose sequence was identical with that of the residues from Gly-6 to Tyr-78 of the prealbumin, except that it had a methionine for a valine at position 25. This corresponded with the position 30 where a valine residues has been reported for the sequence of the normal plasma prealbumin.

Amino Acid Sequence↗
PubMed1984

Immunocytochemical demonstration of beta-endorphin and beta-lipotropin in cultured human spinal ganglion neurons.

Human fetal spinal ganglion neurons isolated and cultured in vitro were found to contain immunoreactive beta-endorphin and beta-lipotropin as demonstrated by immunoperoxidase and immunofluorescence techniques. The specificity of the immunoreactions was confirmed by the negative staining by prior absorption of the specific antisera with added peptides. The culture system described may provide a valuable model system in which cellular mechanism underlying the functions of opioid peptides can be investigated.

Cells, Cultured↗
PubMed1984

Ontogenetic development of the specific [3H]nitrendipine binding sites in the rat whole brain.

[3H]Nitrendipine binding sites are localized much more in the synaptosomal membrane than in the mitochondrial and microsomal membranes. To use a whole homogenate (crude membrane fraction) for the purpose of observing nitrendipine binding sites in the synaptosomal membrane instead of P2-B fraction has its reason. The Bmax of specific nitrendipine binding in the rat brain increases linearly until it reaches to the adult level after birth. High affinity binding at early developmental stages shifts to low affinity after the 7 day postnatal stage. Autoradiographically, nitrendipine binding sites are rich in the interpeduncular nucleus, olfactory bulb, hippocampus and superior colliculus in an adult rat. In autoradiography, the density in the hippocampus increases gradually until it reaches the adult level at the 28 day postnatal stage.

Animals↗